This invention relates to troughing for molten metals and more particularly it relates to heated troughing for flowing molten metal such as molten aluminum from one station to another.
Conventional troughing used for conveying molten aluminum from a molten aluminum source such as a holding furnace to a work station such as a degasser or caster is either not heated or if heated, utilizes radiant heaters such as glow bars which radiate heat from above the surface of the molten metal. If no heaters are used in the troughing, then the distance the metal can be conveyed is limited or the molten metal must be superheated to compensate for the loss in temperature, with its attendant problems such as skim generation. Radiant heaters have the problem of short service life because they are exposed to aluminum vapors, splashing of molten aluminum and mechanical abuse. Also, radiant heaters have the problem that they produce local heating of the surface of the molten metal in the troughing and deposition of a metal skim on the sidewalls of the troughing which contributes to oxide formation. Thus, it can be seen that there is a great need for an improved troughing for conveying molten metal such as molten aluminum which overcomes these problems. This invention provides such an improved troughing.
It is an object of this invention to provide an improved refractory troughing.
It is another object of this invention to provide an improved heated trough member for conveying molten metal such as molten aluminum.
It is a further object of this invention to provide a heated refractory trough for flowing molten aluminum from a molten aluminum source to a work station such as a degasser.
These and other objects will become apparent from a reading of the specification and claims appended hereto.
In accordance with these objects, there is provided a method of heating molten aluminum flowing in a heated trough member comprising the steps of providing a source of molten aluminum and providing a trough member comprised of a first side and a second side, the first and the second sides having outside surfaces, the sides formed from a ceramic material resistant to attack by molten aluminum. The first side and second side have heating element receptacles provided therein preferably with protection tubes provided in the receptacles. The protection tubes are comprised of a refractory selected from the group consisting of mullite, boron nitride, silicon nitride, silicon carbide, graphite, silicon aluminum oxynitride or a metal selected from Kovar(copyright) and titanium. Electric heating elements are positioned in the tubes. Molten aluminum is flowed along the trough member from the source and electric power is passed to the heating elements to heat the molten aluminum as it flows along the trough member.
Further, the invention comprises an electric heating assembly having improved heat transfer, the heater comprised of a receptacle for containing amalgam heat transfer media. An amalgam heat transfer media is provided in the receptacle for purposes of heat transfer. An electric heating element is located in the amalgam. When the amalgam reaches a solidified condition, a receptacle or mold is not required for the electric heating assembly.